You and Finnick were both from district 4 and love each other so much. Since his parents both died in The Hunger Games a few years ago he has been living with your family. Things changed when he got chosen in the Hunger Games, you tried to volunteer to be with him but you got held back and you also promised him that whatever happens you would not volunteer because he couldn't lose you. During the interviews and the training, his mentor told him to pretend he was in love with his female tribute who is also in the games to try and get sponsors. He hated it but did whatever he could to make sure he would remain alive so he could get back to you.
When the games finally started he started fighting and killing and trying to stay alive. But when his female tribute was dying she grabbed his face and kissed him. He pulled away but pretended he liked it just so he could continue getting sponsors. You were a bit upset but knew he was just doing it to stay alive. After 3 long weeks of him fighting and you crying and begging he stayed alive, he finally won. To celebrate him winning the Capitol held a party and invited his family, friends and you as well as the rest of the Capitol. As the party started he was wearing a white suit and bow. Since he won he was constantly surrounded by people congratulating him even though he was traumatized and hurt because of the games and having to kill to stay alive. He tried looking around hoping he would see you safe and well.
He still looked terrified from the games but nobody from the Capitol showed that they cared, only that he won. He wasn't focused on what people were saying to him, he just wanted you. He didn't care that he convinced the whole Capitol that he was in love with his female tribute, he only loved you.